Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

Posted by Chip Stratton on Feb 10, 2011; 1:39am
URL: http://elecraft.85.s1.nabble.com/KX1-Variation-in-driver-transistors-e-g-2SC2166-tp6010045p6010262.html

Thanks Leigh & Don,

I'm not as concerned about maxing output, though getting 4 watts on 20
meters (like I'm getting on 80 meters) would be nice. I do like to
experiment a little, so trying the 2SC5739 would be interesting.

I am interested getting some idea about part to part variability. I have a
lot of experience with LEDs and the variability they exhibit coming off the
assembly line, and am wondering if other semiconductor devices - like the
2SC2166 - show similar variability in efficiencies?

Thanks,
Chip
AE5KA

On Wed, Feb 9, 2011 at 7:22 PM, Don Wilhelm <[hidden email]> wrote:

>  Leigh,
>
> Elecraft is currently shipping KX1s with the 2SC2166 again.  I have
> built 4 in the last month and all 4 have that transistor.
>
> The thermal pad provides better heat conduction and should not be
> eliminated if a plastic tab transistor is used - only the shoulder
> washer is eliminated.
>
> 73,
> Don W3FPR
>
> On 2/9/2011 7:21 PM, Leigh L. Klotz Jr WA5ZNU wrote:
> > Here's some info to read:
> >    http://elecraft.365791.n2.nabble.com/KX1-Q6-question-td662532.html
> > and here, in this erratum superseded by the revision E manual which shows
> > the changeover:
> >    http://www.elecraft.com/manual/KX1_Owners_Manual_Errata_Rev_D-1.pdf
> >
> > It seems that Elecraft went from a 2SC2166 to a 2SC5739 for RoHS
> compliance.
> >
> > A side benefit is that the new part eliminates a thermal pad, shoulder
> > washer, and thus a potential for a short from the KX1 build.
> >
> > Some have reported improved output on 20M with this part, albeit with the
> > usual warnings about too much power causing you trouble later if you
> don't
> > have a great match to your antenna, a strong possibility under the KX1
> > normal operating conditions.
> >
> > Leigh/WA5ZNU
> >
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